1. Field of the Invention
The present invention relates to a motor and a method of manufacturing the motor.
2. Description of the Related Art
There is a known method in which a straight core defined by laminated steel sheets is bent into an annular shape to define a stator core of a motor. A known motor in which such a straight core is used is described, for example, in JP-A H11-069738. A technique of bending laminated punched-out plates into an annular shape to define a stator core is described in JP-A H11-069738 (see paragraph [0003] of JP-A H11-069738). In addition, JP-A H11-069738 notes that a folding portion including a V-shaped cut is defined in a portion of a back yoke between adjacent teeth (see paragraphs [0016], [0026], and [0031] of JP-A H11-069738).
The aforementioned structure described in JP-A H11-069738 has a problem in that magnetic reluctance is increased in each folding portion including the cut. Moreover, as illustrated in the accompanying drawings of JP-A H11-069738, a through hole having a substantially circular shape in a plan view is defined at a tip portion of the cut in the straight core in order to reduce resistance when the straight core is bent into the annular shape. The through hole remains as an opening even after the straight core is bent into the annular shape to define a stator core. This opening causes an additional increase in the magnetic reluctance in the folding portion. As a result, magnetic flux may be disturbed between the adjacent teeth.